1. Field of the Invention
The present invention relates to a method for fanning multi-ply sheets and an adhesive composition therefor.
2. Description of the Prior Art
Japanese Pat. Publication No. 3569/71, Japanese Pat. Publication Nos. 40464/1973, 7634/1975, etc., describe in detail methods for fanning the sheets of each set of multi-ply sheets of, e.g., pressure-sensitive copying papers (described in, e.g., U.S. Pat. Nos. 2,711,375; 2,712,507; 2,730,456; 2,730,457; 3,418,250; 3,432,327; etc.) and an adhesive composition therefor.
According to the prior art, gelatin, gelatin derivatives, gelatin degradation products, or a mixture thereof with an aqueous emulsion of resin (i.e., high polymer latex) are used as an adhesive component.
However, gelatins tend to decompose and undergo great changes in viscosity depending upon the temperature. Therefore, adhesives containing gelatins have failed to attain the desired characteristics with respect to storability, adhesiveness and separability. (The term "separability" designates the ease in fanning the sheets of each set. When fanning can be effected well, the separability is said to be good, whereas when fanning is difficult, separability is said to be poor.) Further, since latexes added for the purpose of increasing the adhesiveness lack separability, even such an adhesive has been desired to be improved as a commercial product.